Phase modulating apparatus



Feb. 17, 1953 M R, LUDWIG 2,629,060

PHASE MODULATING APPARATUS Filed OC'. 50, 1950 mms/roza. /5. 2 MERLE R. LUDWIG -paratus wherein it is desired =to have 'ting network l2.

Patented Feb. 17, 1953 .PATENT OFFICE .PHASE `MODULATING l APPARATUS Mele1&3Llitu'fig,` Minneap'oiis, Minn., assigner to .'Minn'eapols-Hcneywell Regulator Company, zMinneapolis, Mimi., a corporation (if-Delaware Applicatien Octcherl), 1950, Serial No. 194,721.

NThe lpresent invention. "is concerned `with -an electro-inechanical phase modulating apparatus llClainis. (Cl. 30V-2e) and moreparticularly aphase modulating apr,.

signals which are phase modulated and varying in phase in opposite directions with respect to .each other.

In certain types 'ci control apparatusjit is necessary that a -phase'modulated signal he provided which will loe varied at a rate which is synchrovnizedwith'the signal which is heing'modulated.

Further, some control vappara-tus requires two phase 'modulated signal'gwhich have "their "phase modulation 'continuously varying 'in opposite'directions 'or senses. kAttempts y"to produce such signals 'by purely "elec-tronic 'means were not too success-ful `andthe resultant apparatus was 'not too satisfactory because ci the difficulty ci synchronizing 'the carrier signal with the modulat- ,ing signal.

vlt is therefore an object or" the vpresent invention to provi'de 'a new and improved electromechanicalphase modulating apparatus.

A further object of the-present inventienfisto provide an improved modulating apparatus wherein the carrier ireqrency is modulated by a frequency which is synchronized withfthe carrier frequency.

'Anotherohject 'of the present invention, is -to provide an improved phase :modulating apparatus 'wherein 'an `electro-rnechanical apparatus 'phase modulates 'a cf alternating current signals `continuously'in an opposite Vsense ordirection.

Still another vobject of the presentinvention is to change two ph-ase modulated. signals which vary in quadrature into pulses ywhich lvary sinusoidally in ytime Vphase relation lwith "respect -lto each "other,

These and otherohjects of the 'pres-ent invention will 'he understood uponfcoiisidei'ing'the iollowing specification and the drawings, lof which:

Figure "1 is -a diagrammatic showing or" 'the present phase vmodulating apparatus; and

Figure'Z is a graphical showing of the electrical signals produced by the apparatus when in 'operation.

Referring rst toFigure'l, the numeral [trepresents a `driving motor which has 'its output 'connectedto drive an alterna-ting 'current gen- A'iirst comprising 'a 'condenser "f3 "connected in vseries with 'a resistor It 'andthe-:second"comprising an 'inductance It connected in se'ries" with a resistor It. The output of the'phasesplitter I`2 is take-n on conductorsfi and 2l when measured with respect to aconmion conductor '22. The phase of the alternating current signal appearing between conductors 2l and 212 is 90 displaced 'from the alternating current signal 'appearing primary windings 39 and t! and a movable vor rotatable armature 32. `The field vwindings 30 and 3! spaced 90 electrical degrees apart or as shown upon-the drawing mechanicaldegrecs.

The output windings' and 32 are fed into 'suitable pulse shaping networks and 34, respectively, which networks are effective to convert the alternating current input into a chain of pulses, each pulse representing one cycle 'of the input signal.

A mechanism for driving the armaturesv 29 and 32 of the control transformers y'2li and 23 respectively 'is a mechanical 'oscillating device sometimes referred-tc 'as a Scotchyoke v'35. This oscillating mechanism comprises a circular driving wheel which carries a pivoted block 3l. rThe -hlock v'Sl is arrangedfor tra'nsverse Inoveinent within a racewa'y 133 'and causes the raicewayt to move up and downin a vertical fdirection, asshown'upon the-drawngfas-'the drivving wheel rotates.

The fraceway 33 is connected to drive a rack 3Q vJhic'hengages api'nion gear slit. For purposes 'of illustration in the drawing, the 'wheel vwith SSG" movementfof the driving wheel will move'l" and will then reverse ack. toits initial. position. vThe driving force for the driving'wheel'i is obtained from the'inotor lil :acting through a suitable gear train lil. The geartrain iii-one 'embodiment of the invention, was arranged to cut down the speed of'tlfi'eoutputof :the motor it) so that v,the 'frequency of oscillation 'of the 'mechanism 3:5 was le the frequency'of thefoutput alternating voltage from -thegenerator IE l Operation When in operation, the 4inotor `lll is :driving both the `generator VI l andthe oscillatingmechanisint. 'fIhe alternating current output from the generator vn vis fedtnmughthe phase split- .ter I2 where the alternating current signal is shifted so that the alternating current voltage between the conductors 2| and 22 is 90 displaced from the signal on conductors 2|] |and 226. The voltage on the conductors 2| and 22 is connected to the primary windings 2l' and 39 on the control transformers 25 and 219 respectively, These connections are so arranged that the sign: nal phasing on fthe primary 21, as viewed upon the drawing, is in phase with respect to the signal phasing on the primary winding 3D. The output vol-tage appearing upon the conductors 20 vand 22 is fed to the primary windings 28 and 3|. The alternating current phasing on the windings 23 and 3|, as viewed upon the drawing, is also the same, but 90 leading with respect to the phasing of windings 21 and 30.

With the armatures 29 and 32 in the position shown upon the drawing, it will be seen that the field arising from the windings 28 and 3| will have no effect upon the output windings 29 and 32, while the primary windings 21 and 30 will be effectively directly coupled to the output windings 29 and 32 respectively.

Referring to Figure 2, the line A represents the alternating current signal or carrier signal appearing upon windings 21 and 30 and, for purposes of explanation, will be considered as the reference signal. Assuming that at the instance that the output windings 29 and 32 are in the position shown upon the drawing and that 'the reference signal is phased so that the valley 59 will be occurring at that instant, there will be a corresponding peak appearing on the output windings 29 and 32, which peak when fed through the pulse forming networks 33 and 34 will appear as pulses represented as and 52 in lines B and C of Figure 2.

As the output windings are rotated by the Scotch yoke mechanism, assuming the next movement of the windings is in a counter-clochwise direction, it will be noted that the winding 29 will be picking up a signal which is effectively 180 reversed from that appearing on winding 32, as concerns signal picked up from primary windings 28 and 3 Thus, the eiTect oi this is to cause the output signal on winding 29 to lead the reference signal while the signal on winding 32 will lag the reference signal. When the next valley 55 occurs in the reference signal, there will be a peak on the output winding 29 which will appear as a pulse 56 on line B of Figure 2, which is advanced in time phase from the valley 55. In the case of the signal on winding 32, the signal will be lagging the reference signal and as a result, the pulse obtained from the corresponding valley 55 will be lagging in time phase as shown at 51 on line C of Figure 2.

When the Scotch yoke mechanism has rotated the windings 29 and 32 one quarter of a revolution, the time phase difference between the output signals of the carrier on windings 29 and 32 will be a maximum. As the mechanism rotates the windings back again to the initial assumed starting position, the time phasing differential will become less and less until it is the same. Upon the Scotch yoke driving the output windings one quarter of a revolution in the opposite direction, the time phasing of the output signals and the timing of the pulses with respect to the reference signal will reverse. Thus, in Figure 2, the valley 60 in the reference signal will represent the return to the initial position and the valley 3i will represent movement in the opposite direction. The pulses 62 and 63, from the respective networks 33 and 34, will be oppositely displaced in time phase from that during the first portion of the operation. Thus, the pulse 62 will be lagging the valley 6| and the pulse 63 will be leading the valley 6 I. This relationship will continue and a maximum difference in phase will be reached when the output windings have been rotated one quarter of a revolution in the present direction from the starting point. The time phase difference will go back to zero upon the Scotch yoke driving the output windings back to the initial position.

Another way of indicating how the phasing of the pulses varies is to draw slope lines intersecting the base of the pulses on lines B and C. When the slope line is vertical, as at 65, 10, and 15 the pulses are in phase. When the slope lines have a negative slope as at 66, 61, 68, and 69, the pulses on line B are leading those on line C and by an amount which is proportional to the slope of the interconnecting lines. When the slope lines have a positive slope as at 1|, 12, 13 and 14, the pulses on line B are lagging those on line C by an amount proportional to the slope of the lines.

With the motor l0 oscillating the armatures 29 and 32 through the mechanism 35 at a frequency which is -ll the frequency of the output voltage from generator it will be seen that the alternating signal or carrier signal from the generator i will be varied in phase as the oscillating mechanism 35 rotates the armatures 29 and 32 in their respective elds of their associated primary windings. The rate of this phase modulation will obviously be dependent upon the frequency of the oscillating mechanism 35 so that by varying the gear train ratio of gear train 4I it is possible to vary the frequency at which the carrier signal is phase modulated by the apparatus. Since motor I0 drives both the generator and the oscillating mechanism 35, the phase modulating signal and carrier will always be synchronized and the pulses on the output of the networks 33 and 34 will be varying in their timing and in directions which are always opposite.

The present electro-mechanical phase modulator produces phase modulated signals which will consistently vary in their respective phase relationship and will not tend to drift but will remain stable as the apparatus is in operation. Further, while the apparatus is arranged for oscillation of the armatures, there may be instances where it is desirable to rotate the armatures more than 180 or even several revolutions. This additional rotation may be obtained by varying the size of the pinion gear 40.

From the foregoing it will be seen that there has been provided a phase modulating apparatus wherein the carrier signal is synchronized with the modulating signal inasmuch as a common driving motor is used to produce the carrier signal as well as the modulating signal. Further, it will be seen that the control apparatus continuously phase modulates the carrier signal and e produces two phase modulated signals which are converted into pulses and are continuously varying in opposite senses or directions. While many modifications will be suggested to those skilled in the art, it is intended that the scope of the present invention be limited solely by the appended claims.

I claim as my invention:

l. Apparatus for phase modulating a pair of electrical signals, comprising, an electrical generator having an alternating output voltage, electrical phase splitting means energized by said generator and having two output signals displaced in phase from each other, a pair of independent control transformers each having a rotatable armature and a pair of eld windings, said eld windings being energized by said two output signals, and mechanical means synchronously rotating said armatures.

2. Apparatus for phase modulating a pair of electrical signals, comprising, an electrical generator having an alternating output voltage, elec trical phase splitting means energized by said generator and having two output signals displaced in phase from each other, a pair ci independent control transformers each having a rotatable armature and a pair o1" field windings, said field windings being energized by said two output signals, and mechanical means sync ronously oscillating each of said rotatable armatures through a predetermined angle.

3. Apparatus for nchronously phase modulating a pair of electrical signals, comprising, an electrical generator having a motor drive means and an electrical alternating output voltage, ele@ trical phase splitting means energized by said generator and having two output signals displaced in phase from each other, a pair of independent control transformers each having a rncvm able armature carrying an output winding and a plurality ci primary each energized by one of said two output signals, mechanical os cillating means connected in d lying relation to 1ers, and means the armatures oi said tran. connecting said motor drive to said oscillating means to synchronize the operation of said generator with the oscillation of said armature.

4. Apparatus for synchronously and oppositely phase modulating a pail` of electrical signals compri-sing, a drive motor, an alternating current generator driven by said motor, a phase splitting cir cuit energized by said generator and having a pair of output signals displaced in phase from each other by 90 electrical degrees, a pair of independent control transformers each having a pair of input primary windings and a rotatable armature carrying an output winding. each ci said primary windings being displaced 90 electrical degrees apart and being energized by one of said output signals, and a mechanical oscillating mechanism driven by said rive motor and connected to drive said armatures so that the electrical phasing of the output signal on the output windings will be varying at a rate dependent upon the rate of oscillation ci said armatures and in opposite directions.

5. Apparatus for synchronously and oppositely phase modulating a pair of electrical signals cornprising, a drive motor, an alternating current generator driven by said motor, a phase splitting circuit energized by said generator and having a pair of output signals displaced in phase from each other by 90 electrical degrees, a pair of control transformers each having a pair of input primary windings and a rotatable armature carrying an output winding', each of said primary windings being displaced 90 electrical degrees apart and being energized by one of said output signals, a mechanical oscillating mechanism arranged to oscillatingly move said armatures so that the phasing of the output signal will vary at a rate dependent upon the rate of oscillation of said armatures and in opposite directions, and gear reduction means connecting said drive motor to said mechanism so that the rate of oscillation of said mechanism will be a suibmultiple of the output frequency of said generator.

6. An alternating current phase modulating apparatus, comprising, a drive motor, a generator driven by said motor and having an alternating output voltage, a control transformer having a plurality of primary windings and a movable armature carrying an output winding, mechanical oscillating means driving said armature, and gear means connecting said motor to said oscillating means to drive said oscillating means at a submultiple frequency of the frequency of said alternating output voltage.

7. An alternating current phase modulating apparatus, comprising, a drive motor, an alternatcurrent generator driven by motor, a control transformer having a pair of mary windings spaced electrical degrees apart, each en ergized by said generator by a voltage which is 90 electrical degrees displaced from the voltage on the other, and a rotatable armature having an output winding, oscillating means for driving said armature through electrical degrees with respect to one of said primary windings, and means including said drive motor for driving said oscillating means at a frequency which is less than the frequency ci said alternating current generator.

il. An alternating current phase modulating apparatus, comprising, a drive motor, an alternating' current generator driven by said motor, a pair of independent control transformers each having a of 'ings spaced 9i? electrical degrecs apa said pair being energized by said generator a voltage which is 9G electrical degrees displaced in phase from the volta-ge on the other, and each having a rotatable armature carrying an output winding, osci lating means for simultaneously driving said armatures through 1S() electrical degrees and in a direction such that the phase on the outputs of said armatures will be varying in opposite directions, and means including said drive motor for d 1iving said oscillating means at a frequency which is less than the frequency of said alternating current generator.

9. An alternator, electrical circuit means deriving from said alternator a pair of voltages in quadrature, a pair of independent control devices arranged to oppcsitely select varying portions of voltages and combine said voltages so that each of said devices has an output whose phase variations vary in a direction opposite that of the other, and means synchronously driving said devices and said alternator,

1d. An alternator, electrical circuit means deriving from said alternator a pair of voltages in quadrature, a pair of independent control devices arranged to oppositely select varying portions of said voltages and each having an output whose phase variations vary in a direction opposite that of the other, and pulse forming means connected to each of said devices to form a chain of pulses with the pulses derived from each device varying in time phase direction opposite that of the other.

MERLE R. LUDWIG.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Name Date Hartley June 21, 1927 Number 

